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[JamesV6CDX]

On the Astra. Put some new plugs in 1000 miles ago, just checked them, and this is the result:

Plug 1 - very white, with a few bright white deposits

Plug 2 - exactly the same.

Plug 3 - very very black. Some traces of wet oil on the spark plug thread.

Plug 4 - very white, with a few white deposits.

Car symptoms - puffing blue oil when revved after idle, or when cold. Doesn't puff oil when kept at high revs.

Spark plug 3 - would you say this blackness could be related to a crap stem seal(s) above this chamber?

Re the other plugs being very white - does this show that it's running lean? Or maybe too hot? (or both?).
Bearing in mind the car spends all it's life on LPG, I'm not even sure if they may be normal.

Compressions are all at 13.5 bar.

Do others agree it's time to take the head off for further investigation?

If I decide to do the piston rings at the same time - can I do this with the engine in the car? Is it literally a case of take sump off, unbolt piston and remove it from the top?

Thanks all, your replies are appreciated. I've never owned an Astra before and after this, possibly never will!

Shame, 'cos it's nice to drive!

[JamesV6CDX]

Interestingly, I just read that white deposits on the end of the plugs can be caused by dodgey stem seals also 

[Ghost]

Normaly the plugs should be light brown in colour, if one is dark it could be stem seal, piston ring or head gasket not to sure but someone will know.
you should be able to take the pistons out with the block still fitted, as long as there is nothing blocking the bottom of the engine ie exhaust or a frame of some sort.

[JamesV6CDX]

Do they come out from the bottom, or the top?

[Ghost]

depending on how far you strip your engine, if you take the crankshaft out you can get them out the bottom. but I would say its easyer to take and put them in the top. you will need a piston ring compressor to put them back in though. ( but you know that already )
www.machinemart.co.uk/shop/product/details/cht257-piston-ring-compressor/path/engine-service-and-re-build-tools

[cem_devecioglu]

James, sooner or later you will take the head off..

so, do it..

[JamesV6CDX]

I've been talking to lots of other astra owners with same issue.

Every time it has been a piston ring 

I am going to change all of the rings on this one. Not a job I've ever done so wish me luck... helpful hints welcome!

I'm assuming, once head and sump off, it's just a case of cleaning bore, undoing the conrod cap from the journal, and pushing piston upwards?

Does the crank need to be in any set position to remove / refit a piston?

[JamesV6CDX]

I also guess the bores will need honing - is this something I can safely do?


Sorry for all the Q's -  I've never removed a piston!

[Ghost]

before you remove piston clean the top of one and c if there is an arrow or direction mark for refitting. and change all pistons rings.

[Omega man 2]

On an omega (guessing the astra is the same) the arrow is pointing to the front (cam belt) end of the engine. Lightly hone the bores and you might as well replace the shell bearings. I'm sure you'll have no problem removing the pistons on a WWD astra with the engine in place, I did it on a mig.

[Kevin Wood]

I would look for evidence of oil running down the valve stems on that cylinder before deciding it's the rings.

Other plug symptoms are fine IMHO on an engine running LPG. You won't get much colour to the plugs.

Kevin

[JamesV6CDX]

I would look for evidence of oil running down the valve stems on that cylinder before deciding it's the rings.

Other plug symptoms are fine IMHO on an engine running LPG. You won't get much colour to the plugs.

Kevin

Well, the head comes off either way - so, I'll check the seals as a first port of call...

If they're obviously the problem, I 'll leave the bottom end alone.

If not, unfortunately, I will have to bite the bullet...

For some reason I percieve piston changing to be a specialist job - I'm sure that's not the case, as long as time and care is taken....

[smoothomega]

Removing and replacing the pistons is a straight forward job as long as care is taken, just be sure to use a good ring compressor and dont break them when you tap the piggies back into the block.

[JamesV6CDX]

How does the ring compressor work - I'm aware it clamps around the rings and the piston then goes into the bore - does the whole assembly, including the compressor, go into the bore?

[Martin_1962]

You pop the piston out by gentle pushing with a wood rob - eg hammer handle.

Clamp up the rings and then gently bash it back in with the wooden hammer handle. Clamp says outside of the bore.

Fit NEW shells - rude not too

[Kevin Wood]

Biggest problem with doing it in-situ is cleanliness IMHO. Honing the bores will create debris. If the engine is totally stripped the block can be washed afterwards. If it's in-situ with the crank in place you need to be careful not to get debris on the crank journals and oilways as this will bu66er the bearings. Cover them with something while honing and clean up thoroughly afterwards.

It might not come to that though.

Kevin

[Martin_1962]

Biggest problem with doing it in-situ is cleanliness IMHO. Honing the bores will create debris. If the engine is totally stripped the block can be washed afterwards. If it's in-situ with the crank in place you need to be careful not to get debris on the crank journals and oilways as this will bu66er the bearings. Cover them with something while honing and clean up thoroughly afterwards.

It might not come to that though.

Kevin

If a bit glazed wet & dry will do

[JamesV6CDX]

Just been looking on youtube -

Quite confident I can do this without a problem - doesn't look too difficult if care is taken.

As Kev says, I'll check stem seals first - but if all appears OK in the head, I'm not re-fitting the head until it's had a new set of rings.

Why is it that if piston rings really are that simple, people make such a fuss and replace what is otherwise a good engine?

[Entwood]

I think its convenience and cost James .. old days we used to re-ring/rebuild engines all the time .. I well remember changing some main bearings on a ford consol with 2 wheels on the verge and the sump dropped without draining the oil !!  It was what you did !!

Labour charges at upwards of £75 an hour would make a full engine out/strip/rebuild/refit so expensive that most garages say stick a new engine in its cheaper and you get a warranty. Add to that the fact that many garages do NOT employ mechanics/engineers  but partially trained spanner monkeys who haven't got a clue beyond component replacement as told by the idiots lantern in the corner .. and it knows nothing either

Engines are built on stands and many jobs are not designed to be done in-situ, our own spark plugs/ HBV being examples of how non-mechanic-friendly the modern design is .... and when you have to dismantle 1/2 a car to change a light bulb ... as some citroens now do ... 

Lastly, manufacturers are deliberately using more and more "special tools" to do simple jobs .. the cost of these, and the training to use them, presents the old-fashioned garage with a major problem ... is it worth buying tools you may only ever use once You can't charge the cost to the customer...

The days when a box of BSF/Whitworth spanners would do 99% of all jobs are, unfortunately, long gone ..

[Kevin Wood]

Added to that, piston rings really should outlast the rest of the car in a standard production engine these days, so it's a relatively rare problem. Once it does occur, the mileage is NCC-1701 territory so the engine is likely to need a full overhaul rather then just a quick hone and some new rings, so it's engine out, machining work, cleaning full set of bearings, seals, etc. Possibly piston replacement too. Not worth the bother when you look at the cost of a recond engine or 1/2 engine. Or, indeed, the likely value of the car by that time.

Kevin